The present invention relates to end cap closure members or welsh plugs adapted for mounting on bearing units, e.g., trolley wheels used in overhead conveyors and the like and, more particularly, to an improved welsh plug or closure member which provides a positive closure, easier removal from a bearing unit, and reuse of the bearing unit.
The invention also relates to a method for removing a welsh plug or closure member of the type disclosed in the present invention and a tool for supporting a trolley wheel and trolley bracket assembly during installation or removal of an end cap closure member or welsh plug to or from the wheel.
It is conventional to provide welsh plugs or end cap closure members substantially permanently mounted on conveyor wheels or other bearing units. Such closure members are designed to exclude dirt and other foreign matter from the interior of the bearing unit as well as to retain grease or lubricants within the bearing unit during operation. In order to reduce repair and maintenance costs, certain users of bearing units and conveyor wheels desire to remove the end cap closure members or welsh plugs from the bearing units for purposes of repair, inspection or routine maintenance on the bearings. The removal of the closure member enables inspection, cleaning of parts and relubrication of the bearing assembly in a manner which, often times, obviates the need for complete replacement of the assembly.
Various removable closure members have been used in the past including a disc-like welsh plug fitted in a recess on the outer race of a bearing unit and retained on the outer race by an annular snap or split ring received in a retaining groove adjacent the recess in which the closure member is fitted. While such structures have adequately prevented contamination of bearings and retention of grease therewithin, it is necessary to provide approximately a one-sixth greater amount of material in the outer race to accommodate the mounting structure for such split ring closure members, in addition to the greater expense involved in manufacturing and assembling two pieces on each bearing unit. Moreover, corrosion or other degradation of the snap ring, retaining grooves, or the closure member itself can make removal of such structures very difficult.
Other welsh plugs or closure members are substantially permanently mounted by pressing them into corresponding recesses on the outer races of bearing units. In order to provide a secure closure of the bearing unit, a tight fit must be accomplished. When removal of such closure members is desired, it has typically been necessary to remove the grease fitting from the head of the trolley bracket, and drive a rod or other implement through the inner race opening against the closure member from the opposite side of the assembly. Such a procedure is time consuming and often results in damage to one or more parts of the bearing assembly preventing its reuse. Moreover, such disassembly of a trolley bracket from the trolley wheel is often impossible when a riveted or swaged type assembly of the bracket to the wheel inner race is used.
Alternately, such closure members have been removed by driving a sharp implement into the surface of the installed closure member and using the implement to remove the closure member. This too has often caused damage to parts of the bearing structure, is difficult to perform, requires a sharpened tool, and many times ruins the tools used to make such a removal. If, in fact, the implement is driven entirely through the closure member, metal fragments can often be expelled into the bearing assembly which could cause premature failure of the unit if it is reused.
In addition, it was often difficult to support the bearing units or trolley wheels during removal of the closure members. Casual support on any available flat surface during the above-described procedures often resulted in indentation of the rolling element race surfaces. Such "Brinelling" occurred from the impact between the race surfaces and the harder, more wear resistant rolling elements. Reuse of the assembly was then impossible.
Accordingly, the present invention was conceived in recognition of and as a solution for the above problems with previously known end cap closure members or welsh plugs and methods for removing same.